Audio frequency regenerator in a musical instrument



m J. H. HAMMOND, JR y fi AUDIO FREQUENCY REGENERATOR IN A MUSICAL INSTRUMENT Original Filed Aug. 8, 1929 INVENTOR. aw W,

ATTORNEX Patented Apr. 28, 1936 AUDIO FREQUENCY REGENERATOR IN A MUSICAL INSTRUMENT John Hays Hammond, Jr., Gloucester, Mass.

Application August 8, 1929, Serial No. 384,284 Renewed February 6, 1931 4 Claims.

This invention relates to musical instruments, and more particularly to a musical instrument having a vibratable element, and to mechanism for amplifying the vibrations of said element at 5 the will of the operator.

According to a preferred form of the invention a piano is provided having a loud speaker mounted adjacent the vibratable elements thereof. A radio receiver may be incorporated in the piano utilizing the loud speaker for radio reception purposes. When using the combined piano and radio receiver for radio reception, the piano may be used as a mechanical filter for eliminating undesirable sounds, such as static. When using the piano as a mechanical filter, the energy delivered to the vibratable elements of the piano by the loud speaker is picked up by suitable pick-up devices and fed back into the input of the audio amplifier of the radio receiver.

If desired, the combined piano and radio receiver may also be used as a regenerative piano, in which case the energy delivered to the vibratable element of the piano by the loud speaker is picked up by suitable pick-up devices and fed back into the audio amplifier of the radio receiver, thus decreasing the damping when the piano is being played by an artist in the ordinary manner.

The invention also consists in certain new and original features of construction and combina- 30 tions of parts hereinafter set forth and claimed.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, the mode of its operation and the manner of its organization may be better understood by referring to the following description taken in connection with the accompanying drawing forming a part thereof, in which Fig. 1 is a side elevation partly in section of a piano with a diagrammatic showing of the amplifying means in accordance with the present invention; and

Fig. 2 is a broken sectional front View showing a modified form of pick-up means.

Like reference characters denote like parts in the several figures of the drawing.

In the following description and in the claims parts will be identified by specific names for convenience, but they are intended to be as generic in their application to similar parts as the art will permit.

Referring to the drawing more in detail, the invention is shown by way of illustration as applied to a grand piano I0 having strings II and a sounding board l2.

for controlling the amplitude of vibrations of the strings in a well known manner.

Located at various points on the sounding board I 2 are a plurality of pickup devices illustrated somewhat diagrammatically by M which are adapted to be actuated by the vibrations of said sounding board and to produce a varying electric current which is applied to transformers IS, the secondaries of which are connected to a plurality of potentiometers l6. Pick-up devices l4 may, for example, be the type disclosed in P. R. Fortin Patent No. 1,689,524, issued October 30, 1928. Said potentiometers are connected in series to a potentiometer 11, the movable contact [8 of which is mounted on a lever l9 which is Said rod carries a collar 22 which cooperates with lever IQ for elevating the same when pedal I3 is depressed. Spring 2| may be employed for normally holding lever 19 in its lower position.

Radio receiver 25 which may be of any well known type as for example, including a radio frequency amplifier 26, a detector section 21, and an audio frequency amplifier 28 may be connected to an antenna 29 through knife switch 30. The output circuit of receiver 25 may be connected to loud speaker 3| by leads 32.

A loud speaker illustrated somewhat diagrammatically by 3| is preferably mounted on or adjacent sounding board l2 and the dead weight of said speaker is taken up by spring 33 which is carried on frame 34 forming a part of the piano.

The speaker 3| may, for example, be of the type illustrated in Fig. 2 of applicants Patent No. 1,893,892, issued January 10, 1933. The variable contact I8 and one side of potentiometer I! are connected through switch 23 across the input circuit of detector section 2! whereby the audio frequency currents produced by pickup devices I 4 may be applied to said detector element, amplified in audio amplifier 28 and used to actuate loud speaker 3|.

tribution thereof. are nodal areas. anti-nodal areas.

Areas where the sand collects Areas free from sand are the Usually there is some part, as for instance, near the corner of the sounding board, which is com paratively dead for all notes of the piano. This would constitute a nodal point for the loud speaker.

Although the anti-nodal points will change with different notes, it has been found that there are certain anti-nodal areas for certain groups of notes. For instance, the bass notes will have one general anti-nodal area, the intermediate notes will have another and the high treble notes will have another. By using a plurality of pick-up devices l4 and locating one at each anti-nodal area, good pick-up is obtained no matter which note of the entire piano scale is struck.

In the operation of the above described system as a radio receiver, switch 30 is closed and the signals are received in receiver 25, amplified at radio frequency in section 26, detected in section 21, amplified at audio frequency in section 28 and. applied to loud speaker 3 I. The reaction of loud speaker 3|, both mechanically and through the compressional waves generated thereby, causes vibrations of strings II and sounding board [2. These vibrations are then picked up by pickup devices I4 and used to generate currents which are then applied to detector section 21 and amplified in audio frequency amplifier 28 and again applied to the loud speaker.

A system of audio frequency regeneration is accordingly provided in which the tones produced by loud speaker 3| are determined by the qualities of the sounding board l2. Furthermore the pickup from the various portions of the sounding board may be independently controlled by the operation of potentiometers l6 and the amount of regeneration may be controlled by potentiometer I! which governs the amount of energy applied to the input circuit of detector section 21.

In operating the system as a piano, switch 30 is open and the piano is actuated in the usual manner. Vibrations of strings II then cause vibrations of sounding board [2 which are picked up by pickup device l4, passed through the detector and audio amplifier of receiver 25 and applied to loud speaker 31 in the manner pointed out above. An audio frequency regeneration is thus obtained which is controlled by the potentiometers l6 and [1. It has been found that when loud pedal I3 is depressed, thereby raising the dampers from the strings I i, there is a tendency for excessive regeneration which would distort the output of the loud speaker. This is prevented by so connecting potentiometer ll across the input circuit of the detector that when loud pedal 13 is depressed the power applied to the detector is decreased. It is obvious that any desired adjustment may be made to secure the proper operating characteristics.

A modified form of pickup device is shown in Fig. 2 in which pickup devices illustrated somewhat diagrammatically by 38 are located adjacent strings II and are actuated by the vibrations of said strings. A plurality of said pickup devices are shown mounted adjacent various groups of strings. It is understood that they would be so constructed as to secure a maximum response to the frequencies of the strings with which they are associated. Such pick-ups may, for example,

' be of the construction shown in Figs. 1, 2 and 3 of applicants Patent No. 1,893,892, referred to above. Pickup devices 38 are connected to transformers I5, the secondaries of which are applied to potentiometers H5 in the manner shown in Fig. 1.

Although a plurality of pickup devices have been shown for both the sounding board and the strings, it is obvious that a single pickup device can be employed if desired.

It is to be noted that the tonal qualities of the sounding board are utilized in controlling the tonal qualities of the music produced by the loud speaker 3|. In fact the sounding board may be considered to operate as a filter for removing undesired tones from the system. At any rate the quality of the tones produced by loud speaker 3| is improved and the volume thereof is amplified by the above described system. It is obvious that the system may be applied to any well known type of radio receiver possessing means for amplifying currents at audio frequency.

While certain novel features of the invention have been shown and described and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. A system for improving the characteristics of received radio selections, comprising a radio receiver having. an audio frequency amplifier stage, a musical instrument having a sounding board, a loud speaker, means mounting said loudspeaker in vibrational coupling with said sounding board, means actuating said loud speaker by oscillatory energy from said amplifier stage, a pick-up device connected to receive vibratory energy from said sounding board and to translate the same into electrical energy, and a circuit adapted to apply said electrical energy from said pick-up device to the in-put circuit of said am plifier stage, whereby the vibrations of. said sounding board caused by received radio selections are again transmitted through said amplifier stage, amplified therein and are again applied to the loud speaker.

2. A system for improving the characteristics of received radio selections comprising a radio receiver having an audio frequency amplifier stage. a musical instrument having a sounding board, a loud speaker, means mounting said loud speaker in vibrational coupling with said sounding board, means actuating said loud speaker by oscillatory energy from said amplifier stage, a plurality of pick-up devices connected to receive vibratory energy from said sounding board and to translate the same into electrical energy and a circuit adapted to apply said electrical energy from said pick-up devices to the in-put circuit of said amplifier stage, whereby the vibrations of said sounding board caused by received radio selections are again transmitted through said amplifier stage, amplified therein and are again applied to the loud speaker.

3. In a tonal system comprising a radio receiver having an audio frequency amplifier stage, a piano having a sounding board and a loud pedal, a loud speaker, means mounting said loud speaker in vibrational coupling with said sounding board, means actuating said speaker by energy from said amplifier stage, a plurality of pick-up devices connected to receive vibrational energy from said sounding board and to translate the same into electrical energy, a circuit adapted to apply said electrical energy from said pick-up devices to the input circuit of said amplifier stage whereby the vibrations of said sounding board are transmitted through said amplifier, amplified therein and are again applied to the loud speaker, means for individually controlling the response of said devices and means in the input circuit of said amplifier and connected to the loud pedal of said piano for decreasing the amount of energy applied to said amplifier stage When the loud. pedal is depressed.

4. In a radio receiving system, means for receiving radio signals, an audio frequency amplifier stage fed thereby, a piano having a sounding 10 board, a sound propagating element actuated by said amplifier stage and in vibrational coupling with said sounding board, a pick-up device connected to receive vibrational energy from said sounding board and to translate the same to electrical energy and a circuit connecting said pickup device to the input of said amplifier stage whereby received sound energy passes regeneratively through said amplifier.

. JOHN HAYS HAMMOND, JR. 

